//======= Copyright (c) Stereolabs Corporation, All rights reserved. ===============

///
/// Basic wireframe shader that can be used for rendering spatial mapping meshes.
///
Shader "Custom/Spatial Mapping/ GeometryWireframe"
{
	Properties
	{
		_WireColor("Wire color", Color) = (1.0, 1.0, 1.0, 1.0)
		_WireThickness("Wire thickness", Range(0, 800)) = 100
	}
		SubShader
	{
		Tags{ "RenderType" = "Opaque" }



		Pass
	{
		Blend SrcAlpha OneMinusSrcAlpha
		ZTest Always
		CGPROGRAM
#pragma vertex vert
#pragma geometry geom
#pragma fragment frag

#pragma target 5.0
#pragma only_renderers d3d11

#include "UnityCG.cginc"

		float4 _WireColor;
	float _WireThickness;

	// Based on approach described in Shader-Based Wireframe Drawing (2008)
	// http://orbit.dtu.dk/en/publications/id(13e2122d-bec7-48de-beca-03ce6ea1c3f1).html

	struct v2g
	{
		float4 viewPos : SV_POSITION;
		UNITY_VERTEX_OUTPUT_STEREO
	};

	v2g vert(appdata_base v)
	{
		UNITY_SETUP_INSTANCE_ID(v);
		v2g o;
		o.viewPos = UnityObjectToClipPos(v.vertex);
		UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
		return o;
	}

	// inverseW is to counteract the effect of perspective-correct interpolation so that the lines
	// look the same thickness regardless of their depth in the scene.
	struct g2f
	{
		float4 viewPos : SV_POSITION;
		float inverseW : TEXCOORD0;
		float3 dist : TEXCOORD1;
		UNITY_VERTEX_OUTPUT_STEREO
	};

	[maxvertexcount(3)]
	void geom(triangle v2g i[3], inout TriangleStream<g2f> triStream)
	{
		// Calculate the vectors that define the triangle from the input points.
		float2 point0 = i[0].viewPos.xy / i[0].viewPos.w;
		float2 point1 = i[1].viewPos.xy / i[1].viewPos.w;
		float2 point2 = i[2].viewPos.xy / i[2].viewPos.w;

		// Calculate the area of the triangle.
		float2 vector0 = point2 - point1;
		float2 vector1 = point2 - point0;
		float2 vector2 = point1 - point0;
		float area = abs(vector1.x * vector2.y - vector1.y * vector2.x);

		float3 distScale[3];
		distScale[0] = float3(area / length(vector0), 0, 0);
		distScale[1] = float3(0, area / length(vector1), 0);
		distScale[2] = float3(0, 0, area / length(vector2));

		float wireScale = 800 - _WireThickness;

		// Output each original vertex with its distance to the opposing line defined
		// by the other two vertices.
		g2f o;

		[unroll]
		for (uint idx = 0; idx < 3; ++idx)
		{
			o.viewPos = i[idx].viewPos;
			o.inverseW = 1.0 / o.viewPos.w;
			o.dist = distScale[idx] * o.viewPos.w * wireScale;
			UNITY_TRANSFER_VERTEX_OUTPUT_STEREO(i[idx], o);
			triStream.Append(o);
		}
	}

	void frag(g2f i, out half4 outColor : SV_Target)
	{
		// Calculate  minimum distance to one of the triangle lines, making sure to correct
		// for perspective-correct interpolation.
		float dist = min(i.dist[0], min(i.dist[1], i.dist[2])) * i.inverseW;

		// Make the intensity of the line very bright along the triangle edges but fall-off very
		// quickly.
		float I = exp2(-2 * dist * dist / 10);

		// Fade out the alpha but not the color so we don't get any weird halo effects from
		// a fade to a different color.
		float4 color = I*_WireColor;
		color.a = I;
		outColor = color;
	}
	ENDCG
	}
	}
		FallBack "Diffuse"
}